Tools used in oil and gas drilling, particularly jarring devices (“jars” see e.g. U.S. Pat. Nos. 9,038,744; 8,151,910, respectively entitled: “Jet Hammer” and “Drilling Jar,” both incorporated by reference) are usually part of the bottom hole assembly (BHA). The BHA is at the lower-end of a drill-string (which is referred to herein as a work string, including both coil tubing and pipe strings; and both as a “string” and a “drill string”). The BHA consists of (from the bottom up in a vertical well) the drill bit, the drill bit sub, optionally, a mud motor (used for driving of the bit hydraulically without rotating the work string), as well as stabilizers, which keep the assembly centered in the hole, a drill collar (heavy, thick-walled tubes used to apply weight to the drill bit) and preferably jars and, as needed, crossovers (adaptors) for fitting together different thread forms on the various components.
Directional drilling is now commonplace, and allows turning a vertical drill string and boring horizontally, or at any angle between horizontal and vertical. Some wells now extend over 10 km from the surface start location, but at a true vertical depth of only 1,600-2,600 m. With directional drilling, and with very deep wells, it's often preferable to place jars at intervals along the string, as well as at the BHA. During drilling of such wells, the drill-string often sticks, and needs to be jarred loose.
Following or in conjunction with the initial drilling, hollow metallic tubes (known as “casings”) may be inserted within the bore to prevent walls of the bore from collapsing. Usually, multiple hollow casings are installed vertically one above the other by screwing ends of adjacent casings with each other. The entire assembly of attached casings is commonly known as a “bore casing.” Once a bore casing is formed, a variety of equipment (including crude oil pumping equipment, preferably coil tubing, as well as sensor equipment) can be installed within the bore casing. In an operational oil well, crude oil is pumped to the surface of the earth from the buried crude oil deposits with the help of pumping equipment installed in the bore casing.
Even inside a casing, however, the coil tubing may bind against the casing inner walls, especially in a deep well. Also, the performance and efficiency of the production is vulnerable to failure of equipment installed within bore casing, or changed conditions within the well bore. Troubleshooting of such problems often requires liberating stuck equipment with a jar, which may be followed by retrieval (or fishing) of equipment within the bore casing.
The coiled tubing rides out on a powered drum and is movable vertically within the bore casing. The jarring device is capable of providing a striking impact (or a shock wave) in both upwards and downwards directions, in order to free trapped equipment or bound tubing.
Often, installed equipment within a well bore casing is held together by interlocking friction fittings. For successful separation of such installed equipment assembly, it is important that the jarring impact is strong enough to overcome shock absorption which may occur due to movement at the friction fittings.
In the jarring device disclosed in U.S. Pat. No. 8,151,910 (the '910 Patent), one exerts, from the surface, either stretch or compression forces on a mandrel, and uses mechanical friction in order to load the potential energy of the stretch or compression forces. Overcoming the friction leads to a sudden release of the mandrel, which generates a significant striking impact against an anvil; which in turn generates a shock wave along the coil tubing, which travels to the stuck equipment or stuck tubing portion.
Another jarring device, disclosed in U.S. Pat. No. 10,267,114 (the '114 Patent; incorporated by reference) uses the principle of sudden release of pressurized fluid to generate mechanical movement and a striking impact. The fluid flow is initially blocked by a deformable sphere, and released when the sphere deforms and travels through the blocked channel in the device. Though this is principle of operation is advantageous in not requiring stretching or compression of the drill string (which may be somewhat more likely to affect the string or other equipment, such as the BHA) the '114 Patent device does not provide storage of a substantial amount of potential energy before release, and would be expected not to generate a significant, or adequate, jarring impact to release highly bound tubing or stuck equipment.
While using the principle of a deformable or dispensable sphere to block fluid flow is a simple, feasible method of jar operation, there is a need for an improved jarring device which provides a stronger jarring impact than the'114 Patent device.